Gastric pyloric gland adenoma resembling a submucosal tumor: A case report.

BACKGROUND Pyloric gland adenoma (PGA) is a recently described and rare tumor. Submucosal tumor (SMT)-like PGA is more difficult to diagnose and differentiate from other submucosal lesions. CASE SUMMARY We present the case of a 69-year-old man with a 10 mm SMT-like elevated lesion with an opening in the upper part of the gastric body, referred to our hospital for further endoscopic treatment. Magnifying endoscopy with narrow-band imaging, endoscopic ultrasonography, and complete endoscopic submucosal dissection were performed on the patient. Histopathological findings revealed tightly packed tubular glands lined with cuboidal or columnar cells that had round-to-oval nuclei containing occasional prominent nucleoli and an eosinophilic cytoplasm similar to that in non-neoplastic gastric pyloric glands. Additionally, immunohistochemical analysis showed positive staining for both mucin 5AC and mucin 6. Therefore, we arrived at the final diagnosis of gastric PGA. Although there was no apparent malignant component in this tumor, PGA has been considered a precancerous disease with a high risk of transformation into adenocarcinoma. CONCLUSION PGA should be considered when detecting gastric SMT-like lesions. Physicians and pathologists should focus on PGA due to its malignant potential.